1. Field of the Invention
The present invention generally relates to a magnetic interface, and applications of the same.
2. Related Art
Radio frequency and microwave integrated circuits (collectively called RFICs herein), include active components and passive components that are printed or deposited on a suitable substrate. The various active and passive components are connected together with transmission lines. Exemplary transmission lines include microstrip transmission line, stripline, and/or co-planar waveguide transmission line.
Active components typically include one or more transistors that require DC bias for proper operation. Examples of active circuits include amplifiers, oscillators, etc. Passive components do not require DC bias for proper operation. Examples of passive components include inductors and capacitors, which can be configured as filters, multiplexers, power dividers, phase shifters, etc., and other passive circuits. Passive components are also incorporated in the bias circuitry of active components.
Inductors are an important building block for many passive components. They can be generally classified into two categories, namely discrete inductors and printed inductors. Discrete inductors (e.g., leaded inductors, surface mounted inductors, and air coil inductors) are generally packaged in containers having terminals that are electrically connected to a substrate using solder or epoxy. In contrast, printed inductors are not packaged in a container. Instead, printed inductors have patterns of conductive material that are printed or deposited directly on the substrate. The patterns of conductive material are often called spiral arms, or traces.
The integration of discrete inductors onto a substrate requires expensive assembly techniques. Therefore, RFICs that have discrete inductors are more costly to manufacture than those using printed inductors. Accordingly, it is desirable to use printed inductors in RFICs whenever possible to minimize cost and assembly time.
Unfortunately, replacing discrete inductors with less expensive printed inductors typically requires a tradeoff in circuit footprint. Conventional printed inductors are typically larger than their discrete inductor counterparts for a given inductance value. Furthermore, printed inductors are typically unshielded, and therefore receive and radiate unintentional electromagnetic radiation through the substrate. As a consequence, conventional printed inductors need to be spaced at a some distance from other electronic components on the substrate in order to minimize electromagnetic interaction with other electronic components (including other inductors).
Therefore, what is needed is a printed inductor configuration that produces a high inductance value, but that minimizes substrate area, and unintentional radiation with other components.